Segments in multiple processes

Following example doesn't work. start_subsegment returns always {:error, :out_of_xray}. Because the subsegment is not on the process which start tracing.

Pay attention when you use Task.Supervisor or GenServer.

segment = AwsExRay.start_tracing(trace, "root_segment_name")

Task.Supervisor.start_child(MyTaskSupervisor, fn ->

  ####################################################################
  # this function is executed on different process as root-segment!!!
  ####################################################################

  current_trace = AwsExRay.start_subsegment("subsegment-name")

  do_some_work()

  case current_trace do
    {:ok, subsegment} ->
      AwsExRay.finish_subsegment(subsegment)

    {:error, :out_of_xray} -> :ok
  end

end)

The solution.

Call AwsExRay.Process.keep_tracing(process_which_starts_tracing) like following

segment = AwsExRay.start_tracing(trace, "root_segment_name")

tracing_pid = self()

Task.Supervisor.start_child(MyTaskSupervisor, fn ->

  AwsExRay.Process.keep_tracing(tracing_pid)

  current_trace = AwsExRay.start_subsegment("subsegment-name")

  do_some_work()

  case current_trace do
    {:ok, subsegment} ->
      AwsExRay.finish_subsegment(subsegment)

    {:error, :out_of_xray} -> :ok
  end

end)